Method and apparatus for entropy encoding using hierarchical data unit, and method and apparatus for decoding

Abstract

Provided are video encoding and decoding methods and apparatuses. The video encoding method includes: encoding a video based on data units having a hierarchical structure; determining a context model used for entropy encoding a syntax element of a data unit based on at least one piece of additional information of the data units; and entropy encoding the syntax element by using the determined context model.

The invention claimed is: 
     
       1. A video decoding method comprising:
 obtaining, from a bitstream, a split transformation flag indicating whether a transformation unit included in a coding unit is split; 
 obtaining a current transformation unit from the coding unit based on the split transformation flag; 
 determining a context model using a context model index determined based on a size of the current transformation unit and a value of a color component index of a picture including the transformation unit, without using any syntax elements from blocks neighboring the coding unit, wherein the color component index is set with respect to a luminance color component, a first chrominance color component, and a second chrominance color component, and the color component index for the luminance color component has a value of zero, the color component index for the first chrominance color component has a value of one, and the color component index for the second chrominance color component has a value of two; 
 obtaining a transformation coefficient flag indicating whether at least one non-zero coefficient is included in a block of the transformation unit by decoding the bitstream using Context Adaptive Binary Arithmetic Coding (CABAC) based on the context model; and 
 obtaining a transformation coefficient included in the current transformation unit based on the transformation coefficient flag, 
 wherein the obtaining the transformation coefficient flag comprises obtaining information indicating a most probable symbol (MPS) based on the context model, 
 wherein the picture is split into a plurality of maximum coding units according to information about a maximum size of the coding unit, 
 a maximum coding unit, of the plurality of maximum coding units, is hierarchically split into one or more coding units of depths including at least one of a current depth and a lower depth according to split information, 
 when the split information indicates a split for the current depth, a coding unit of the current depth is split into four coding units of the lower depth, independently from neighboring coding units, and 
 
       when the split information indicates a non-split for the current depth, one or more transformation units are obtained from the coding unit of the current depth. 
     
     
       2. The video decoding method of  claim 1 ,
 wherein the luminance color component is Y, the first chrominance color component is Cb, and the second chrominance color component is Cr.